What Is Nano Optics

In this chapter we introduce the concepts of propagating and evanescent waves. The removal of the latter waves in conventional optics is responsible for the diffraction limit of light, which we will explain in terms of the scalar wave equation. A discussion within the framework of Maxwell’s equations will be given in later parts of this book. We start by introducing the one-dimensional scalar wave equation, and then ponder on the generalization to higher dimensions. Many of these concepts will be familiar to most readers, but are repeated here for clarity. Once we have set up the stage, we will focus on the role of evanescent waves and how to live with or without them in the field of nano optics. We conclude the chapter with a brief summary of Chaps. 2– 11 forming the first part of this book.